SU1326892A1 - Method of measuring flow rate - Google Patents

Abstract

This invention relates to an ultrasonic measuring technique. The purpose of the invention is to improve the measurement accuracy. A device that implements the method contains an acoustic channel 1, a switch 2, a driver amplifier 3, a multiplier 4. elements 5 and 6, a strobe pulse generator 7, a counter 8, a receiving register 9, a digital indicator 10 and a delay circuit 11. The introduction of new elements and the formation of new connections between the elements of the device eliminates the influence of inter-contact asymmetry on the flow measurement result, if the sound speed is represented by a second-degree polynomial, which increases the duration of the measuring strobe and provides greater measurement sensitivity. 2 Il. u (L 00 th O5 00 co th

Description

The invention relates to an ultrasonic measuring technique and can be used to measure the flow of liquids and gases.

The purpose of the invention is to improve the measurement accuracy.

FIG. 1 shows a functional diagram of the device that implements the method; in fig. 2 - timing diagrams illustrating the method.

The device contains an acoustic channel 1, a switch 2 and the amplifier-shaper 3, forming a synchrocard circuit. A separate output amplifier amplifier 3 is connected to the input of a pulse multiplier 4 frequency, the output of which is connected to the inputs of elements 5 and 6, implementing logical I. Other inputs of elements 5 and 6 are connected to anti-phase outputs a and b of the generator 7 strobe pulses. Control yihiy input of switch 2 is connected to one of the outputs of generator 7 (in the diagram - to output a). The output of element 5 is connected to the summing input of the reversing counter 8, and the output of element 6 is connected to the subtractive input of the same counter. The outputs of the bits of the counter 8 are connected to the information inputs of the receiving register 9, the outputs of which are connected to the digital indicator 10. The additional output to the generator 7 is connected to the read input of the register 9 and through the delay circuit 11 to the input of the zero setting of the counter 8.

The essence of the method consists in periodically changing the relative direction of the ultrasonic pulses and the controlled flow in the acoustic channel 1 by means of the switch 2 and determining the flow rate by the difference in the frequency of the synchro-pulse pulses following and against the flow. Switch 2 is switched at times equal to 0.25 and 0.75 measurement cycles, as well as at the end of each cycle. Record in the register 9 information about the flow produced at the end of each second cycle with the aim of pairwise averaging the measurement results.

The method is carried out as follows.

When the power is turned on, the amplifier-shaper 3 is launched and outputs a short impulse through the switch 2 to the piezoelectric element, which radiates an ultrasonic pulse to the region of the channel 1 filled with the controlled medium. After reaching the opposite piezoelectric element, the pulse is converted into an electric one, which, having passed through the switch 2 to the amplifier

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Driver 3, starts it again. The process then repeats.

To measure the difference in frequency, the pulses of the amplifier 3, multiplied by the repetition frequency of multiplier 4, are fed to the inputs of the reversing counter 8 gated by elements 5 and 6. The output of the strobe pulses by the generator 7 is performed according to the diagrams in FIG. 2 in accordance with the switching algorithm of switch 2 described above. Anti-phase strobe pulses of generator 7 alternately open elements 5 and 6 to pass multiplied pulses from the synchrock to counter 8. In addition, the strobe pulses control switch 2 in such a way that Element 5 is exposed to ultrasonic pulses in the flow, while element 6 is emitted against the flow, therefore, when the controlled medium moves, the summing input of counter 8 during the strobe time receives several more pulses than on ayuschy. The difference in the number of these pulses accumulates on the counter 8. To fix this difference, corresponding to the desired flow, averaged over a couple of measurement cycles, generator 7 generates and outputs additional output pulses at the end of each second measurement cycle. These pulses record the difference number from counter 8 to register 9, and also (after a delay of 1-2 x in delay circuit 11) to reset counter 8. Periodic flow information from register 9 is displayed on indicator 10.

The advantage of the proposed method (in comparison with the known ones) is the almost complete elimination of the influence of inter-contact asymmetry on the flow measurement result, if the sound speed is represented by a second-degree polynomial, which increases the duration of the measuring gate and, as a result, provides more measuring sensitivity.

Claims (1)

Invention Formula The method of measuring the flow, consisting in the emission of ultrasonic pulses along the stream, periodically changing the relative direction of the pulses and the flow at times equal to 0.25 and 0.75 cycles of measuring the difference between the frequencies of the synchro-ring in the flow and against it, in order to improve the accuracy measurements, after each cycle, the relative direction of the pulses and the flow is changed, and the flow rate is determined by the average flow rate in two adjacent cycles. la t FIG. 2